SM 25x275 [2xM8] / N42 - magnetic separator

Strengths as well as weaknesses of rare earth magnets.

Besides their tremendous pulling force, neodymium magnets offer the following advantages:

• Their strength is durable, and after around 10 years it decreases only by ~1% (theoretically),
• They are resistant to demagnetization induced by presence of other magnetic fields,
• Thanks to the shiny finish, the plating of Ni-Cu-Ni, gold-plated, or silver gives an visually attractive appearance,
• Neodymium magnets achieve maximum magnetic induction on a small surface, which increases force concentration,
• Due to their durability and thermal resistance, neodymium magnets are capable of operate (depending on the form) even at high temperatures reaching 230°C or more...
• Considering the option of flexible shaping and adaptation to custom requirements, NdFeB magnets can be created in a broad palette of geometric configurations, which amplifies use scope,
• Wide application in electronics industry – they find application in magnetic memories, drive modules, medical equipment, and multitasking production systems.
• Thanks to their power density, small magnets offer high operating force, in miniature format,

Disadvantages of NdFeB magnets:

• To avoid cracks under impact, we suggest using special steel holders. Such a solution secures the magnet and simultaneously increases its durability.
• Neodymium magnets decrease their strength under the influence of heating. As soon as 80°C is exceeded, many of them start losing their force. Therefore, we recommend our special magnets marked [AH], which maintain stability even at temperatures up to 230°C
• Due to the susceptibility of magnets to corrosion in a humid environment, we suggest using waterproof magnets made of rubber, plastic or other material stable to moisture, when using outdoors
• We recommend a housing - magnetic holder, due to difficulties in producing nuts inside the magnet and complex forms.
• Health risk to health – tiny shards of magnets pose a threat, if swallowed, which becomes key in the context of child safety. Furthermore, small elements of these products are able to be problematic in diagnostics medical in case of swallowing.
• With large orders the cost of neodymium magnets can be a barrier,

Maximum holding power of the magnet – what it depends on?

Information about lifting capacity was determined for ideal contact conditions, taking into account:

• using a plate made of mild steel, acting as a circuit closing element
• whose thickness reaches at least 10 mm
• with an polished touching surface
• without any clearance between the magnet and steel
• under vertical force direction (90-degree angle)
• in neutral thermal conditions

Determinants of lifting force in real conditions

It is worth knowing that the working load may be lower influenced by the following factors, in order of importance:

• Distance – existence of any layer (rust, dirt, gap) acts as an insulator, which reduces power rapidly (even by 50% at 0.5 mm).
• Force direction – remember that the magnet has greatest strength perpendicularly. Under shear forces, the capacity drops drastically, often to levels of 20-30% of the maximum value.
• Substrate thickness – to utilize 100% power, the steel must be sufficiently thick. Paper-thin metal limits the lifting capacity (the magnet "punches through" it).
• Material composition – different alloys reacts the same. High carbon content weaken the interaction with the magnet.
• Base smoothness – the more even the surface, the better the adhesion and higher the lifting capacity. Roughness acts like micro-gaps.
• Temperature influence – high temperature weakens magnetic field. Exceeding the limit temperature can permanently damage the magnet.

* Holding force was measured on a smooth steel plate of 20 mm thickness, when the force acted perpendicularly, whereas under shearing force the holding force is lower. Moreover, even a minimal clearance {between} the magnet and the plate decreases the load capacity.